Combustion Characteristics Of Flame-Retardant Polycarbonate And Its Potential Fire Hazard Evaluation

Polycarbonate(PC)has high strength,impact resistance,fatigue resistance,abrasion resistance,and aging resistance.It is widely used in many fields such as automobile manufacturing,aerospace,and medical equipment.However,PC will drip and produce a large amount of toxic smoke when it burns,which poses a great fire hazard.In response to the above problems,this paper designs 5-secondary amino-2-naphthalene sulfonate hexa-substituted hexachlorocyclic triphosphazene flame retardant(N-P-S synergistic flame retardant),and it is compounded with potassium perfluorobutane sulfonate(PPFBS)and phenyl silicone resin(PSR)for PC flame retardant.Study the pyrolysis and combustion characteristics of PC and its composites under different heating rates and environmental heat radiation flux;analyze the property and mechanism of various types of flame retardants;establish an analytic hierarchy model for comprehensive fire safety evaluation of PC and its composites.The specific research content is as follows:1.A new type of N-P-S synergistic flame retardant was synthesized through substitution reaction.This work compounded with PPFBS,PSR and anti-dripping agent for flame-retardant PC.When the addition amount of N-P-S synergistic flame retardant is 0.3 wt%,the addition amount of PPFBS is 0.1 wt%,and the addition amount of PSR is 3 wt%,the flame retardant performance of PC is the best.2.Based on the pyrolysis kinetics theory,the characteristics of PC and its flame-retardant composites at different heating rates were studied.Through the calculation and fitting,PC pyrolysis mechanism is random nucleation and subsequent growth,which satisfies the Aevrami-Erofeev(A2)equation,and the reaction order is 1/2.It can be proved that N-P-S synergistic flame retardant will increase initial decomposition temperature and residual carbon content of the material,and keep the activation energy value at high level;PPFBS has been shown to promote the pyrolysis of matrix in various aspects;due to the migration effect of PSR,the decomposition of this sample will be promoted at low heating rates,and be restrained at high rates.3.Through cone calorimetry test,the combustion characteristics of different flame retardant systems with heat radiation are obtained.After fitting the experimental data,it can be judged that PC and its flame-retardant composites conform to the thermal thick material model.Among them,N-P-S synergistic flame retardant can reduce the smoke production and heat release rate peak of PC,and significantly extend the time for the total CO emission;PPFBS will effectively reduce the heat release and toxic gas produced when PC burned at 25 kW/m2,but it has a combustion-supporting act under high radiation flux;PSR has outstanding effects in reducing heat release and suppressing smoke toxicity.4.Based on the theory of analytic hierarchy process,a comprehensive evaluation system for the fire safety of secondary PC composite materials was established(including 6 primary indicators and 22 secondary indicators).The fire safety index of PC and its flame-retardant composites were in the order of:PSR flame retardant sample>N-P-S synergistic flame retardant sample>PPFBS flame retardant sample>PC sample.At the same time,the influence of N-P-S,PSR,and PPFBS flame retardants on fire safety performance of PC materials was revealed.In this study,after analyzing the pyrolysis and combustion influence laws of the three PC flame retardant systems at the optimal addition levels,the test results were substituted into the established comprehensive evaluation system to compare:N-P-S synergistic flame retardant has outstanding advantages over sulfonate flame retardant in terms of suppressing ignition,fire spread and smoke toxicity,but it char formation and reduction of smoke output still need to be improved compared with PSR flame retardants.